1. Field of the Invention
The present invention relates to a vehicle body frame structure of a saddle-riding type vehicle.
2. Description of Background Art
A known structure for a vehicle body frame of a saddle-riding type vehicle includes a front portion frame that is formed from a head pipe, a pair of left and right main frames, a bracket, and a cross member. Specifically, the left and right main frames extend downwardly toward the rear from the head pipe. The bracket connects rear ends of the left and right main frames. The cross member connects front portions of the left and right main frames (See, for example, Japanese Patent Laid-Open No. 2001-71975).
Another known structure for a vehicle body frame of a saddle-riding type vehicle forms the vehicle body frame from a head pipe, left and right lower pipes, left and right rear pipes, left and right upper pipes, an upper connection pipe, and a bracket. Specifically, the left and right lower pipes have front ends welded to the head pipe and rear ends welded to central portions of left and right upper pipes. The left and right rear pipes have front ends welded to rear portions of the left and right lower pipes and rear ends welded to the front portions of rear portions of the left and right upper pipes. The left and right upper pipes have front ends welded to the left and right lower pipes and are connected in a vehicle width direction by three bridge pipes. The upper connection pipe has a front end welded to the head pipe and a rear end welded to a center bridge pipe. The bracket is welded to the rear portions of the left and right lower pipes (See, for example, Japanese Utility Model Publication No. Sho 63-38155).
In the known vehicle body frame structure of the saddle-riding type vehicle disclosed in Japanese Patent Laid-Open No. 2001-71975, the cross member does enhance a bending stiffness of the vehicle body frame; however, because the cross member is disposed across the front portions of the left and right main frames, it is difficult to increase the capacity of an air cleaner.
In the known vehicle body frame structure of the saddle-riding type vehicle disclosed in Japanese Utility Model Publication No. Sho 63-38155, the bridge pipes and the upper connection pipe are disposed on the vehicle body frame. This makes it difficult to increase the capacity of the air cleaner.